The Healthy Guide to Lasting Weight Loss

It turns out that how you go about slimming down has a profound impact—all too often negative—on your chances of success. The latest findings offer some clearer-than-ever guidelines on how to sort fad diets from healthy, sustainable ways to achieve your best weight.

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So what's the message for women ­trying to lose weight?" asks ­Marcelle Pick, nurse practitioner and author of The Core Balance Diet. "That you're doomed, and—good luck?" Pick thinks the story is more nuanced and not as grim as all that, but she's not surprised when ­people are disheartened, particularly in the wake of a study published last ­October in The New England Journal of ­Medicine, the ­latest and most telling blow against the ­notion that American women in their ­twenties, whose average weight climbed about 30 pounds from 1960 to 2000, could slim back down with just a little more will­power. In that study, conducted at the Univer­sity of Melbourne in Australia, subjects who lost more than 10 percent of their body weight experienced a corresponding change in ­crucial appetite-regulating ­hormones such as leptin—and they ­never returned to normal levels during the remainder of the yearlong research period.

Why is that such a big deal? Produced by fat cells, leptin tells your brain's hypo­thalamus whether your body's energy reserves are sufficient. Low leptin signals that you need to build up your fat stores, and your brain orchestrates a response—"I'm hungry!"—to compel you to regain weight, even if that's the last thing your conscious mind wants as you endeavor to maintain post-diet weight loss.

Or consider a study that will likely come out later this year. Eric Ravussin, PhD, a leading weight researcher at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, measured the contestants on TV's The Biggest Loser and found their leptin levels to be in the tank (six had levels that didn't even register on the standard measurement test)—which means the odds are their hunger pangs will be so intense that they'll qualify for The Biggest Regainer in a few years.

The physiological affront is actually a one-two punch. After significant weight loss, not only does our hunger increase but our metabolism slows, so we hold on that much more tightly to each calorie we consume. Researchers at Columbia University have found that people who, like those in the Melbourne study, lose at least 10 percent of total body weight burn 300 fewer calories a day on average than they did before the weight came off. (No one has looked at the metabolic effects of milder weight loss.) So at the same time that your brain is ordering you to eat more, you must eat less to maintain that slimmed-down physique. The woman who goes from 170 to 130 pounds through assiduous dieting and exercise may look just like her friend who's always weighed 130—same shape, same percentage of body fat—but inside, her "fat brain" is still doing everything in its power to send her body back to Fatville. Hence the dirty not-so-little secret of weight loss: It's not that hard to lose weight—motivated dieters do it all the time—but maintaining that loss is a bitch, with success rates as low as 2 percent or as "high" as 20 percent, depending on which studies you choose to believe.

The enemy here is summed up in the concept of the "set point": simply put, the weight, give or take a few pounds, that your body wants to be. If you drop below your set point—by more than 10 percent, anyway—it will "defend" itself by increasing your ­hunger and lowering your metabolism, which leads to your feeling cranky, chilly, sluggish, and food-obsessed. (In the classic set-point experiment done during World War II, male volunteers at the Univer­sity of Minnesota endured a semi­starvation diet for the better part of a year. How did this regimen affect them behaviorally? Mostly they sat around complaining and sharing favorite food fantasies.)

The precisely wrong way to go about ­losing weight, then, is to dive right past your set point by shedding weight quickly, cutting back calories to a level you ­simply can't tolerate for the long haul, and ­setting yourself up for the near-inevitable regain. This sad set-point saga is repeated over and over again in New York Times ­reporter Gina Kolata's 2007 book, Rethinking Thin, as she chronicles the failed (and, in fact, apparently doomed) efforts of four deter­mined dieters to keep off the weight they've succeeded in losing.

Indeed, in a new book out this January, Why Women Need Fat, coauthor ­William Lassek, MD, an epidemiologist at the University of Pittsburgh, goes so far as to ­argue that not only do people end up yo-yo dieting ­because they gain everything back, but that yo-yo dieting itself is a main ­reason why American women are, on aver­age, 20 pounds heavier than their Euro­pean counter­parts. Analyzing a ­number of studies, Lassek found that women who frequently diet are heavier than those who never bothered in the first place.

"The tragedy of dieting is that the more you diet," Lassek soberly concludes, "the heavier you become." Whether yo-yo dieting is actually worse than doing nothing is far from a settled question in the field, but Lassek explains his position with elegant set-point logic: After enduring a series of strict diets (which to some degree mimic the famines in our evolutionary history to which our bodies, the theory goes, ­developed metabolic survival responses), your body ends up demanding greater fat reserves to buffer itself against whatever undernourishment might be coming next.

But back to Marcelle Pick's question. Is shedding ­unwanted pounds completely ­hopeless? No. Even Lassek believes that if you under­stand your set point, you can work within its range to achieve the best weight you're ­capable of maintaining—­becoming somewhat less heavy and considerably more healthy. (Those who have it hardest are the rela­tively few who are genetically programmed to be obese; this group faces a seriously uphill battle, though one that can be won, Lassek and other experts believe.)

The first obstacle we face, however, is that, constantly tempted by high-­calorie snacks and junk-food meals, many of us have lost sight of the lowest set-point weight that our genes will readily allow us to ­sustain; a more accu­rate term for where we end up, suggests Ravussin, is a ­"settling point"—the weight that our genes and ­current lifestyles (which is to say, our ­habits of diet and exercise) conspire to ­defend. He points to his study of Pima ­Indians. Pimas who retain a traditional way of life and cuisine in Mexico are still lean and fit, but their genetically near-­identical North American cousins have found a new ­settling point—and an alarming inci­dence of obesity—courtesy of fattier foods, refined carbohydrates, and a more sedentary lifestyle. (In his 2009 book, The End of Overeating, former FDA commissioner ­David Kessler, MD, essentially accuses the food industry of hooking us on cheap-to-produce processed foods high in fat, sugar, and salt. He suggests an exercise to relocate our real hunger level: Cut back your meal portions by half, then see how you feel 30 minutes and then 90 minutes after eating.)

I can come up with an example closer to home. Some 25 years ago, my sister-in-law, Naomi Moriyama, left her native ­Japan to finish college. When she returned home after two years of living and eating like an American coed, her family was shocked to see she'd added more than 25 pounds to her compact 5'2" frame. She went back to eating the way she always had—lots of fish and veggies, smaller ­portions, far less junk food—and the weight dropped off in a ­matter of weeks, an experience that she put to good use in writing her 2005 book, Japanese Women Don't Get Old or Fat.

On the other hand, my wife, Kate, a sixth-­generation Irish-American, was dealt those hang-on-to-the-last-­potato genes. Unless she pays undying ­attention to what she eats and how much she exercises, the ­unwanted weight piles on, her ­hormonal and neural circuitry a one-woman hunger museum. Moriyama's ­settling point was temporarily thrown out of whack because of a lifestyle change; Kate does battle with her physiological set point on a daily basis.

How can you tease apart your set point from your settling point so you can gauge how far you might be able to knock down your weight by adopting a healthier ­diet-and-exercise lifestyle? Lassek offers a ­couple of rough-and-ready formulas: You can "eyeball it"—look at photos of ­older ­female relatives taken when they were about your age, and ask them how much they weighed back then. Or check out the handy-dandy chart in Why Women Need Fat and see how your present weight translates to your hypothetical weight in the 1960s, pre–obesity epidemic. For a ­woman ­under 30, her 150 pounds is equivalent to—­presto-chango—127 pounds back in the '60s; 180 pounds now was 140 then. (No one really knows how long we can carry extra pounds before they become the new normal, jealously protected by the body's metabolism.)

I consulted with three prominent clinicians in the weight-loss trenches—Pick, Marc David (author of The Slow Down Diet), and Kathie Madonna Swift (­coauthor, with a Johns Hopkins doctor, of The Inside Tract: Your Good Gut Guide to Great Digestive Health). Pick and Swift often use a set- or settling-point framework to help guide their clients toward their lowest sustainable weight. Their ­clients are often prescribed a whole-food, heavy-on-the-fruits-and-veggies diet, and they lose weight slowly, without ever "going on a diet" in the classic American way—or ever feeling unduly hungry.

"Fiber is magic," Swift says. "A lot of my clients are surprised: 'Oh my God, I'm not hungry all the time!' " (Pick, who ­struggled with her own weight for years, says she drinks two smoothies with chia seeds each day to keep hunger at bay.)

The researcher who distilled the idea that you can lose weight by ­working with, not against, your set point was Harvard's George Blackburn, MD/PhD, a grand old man of diet science who recalled for me his ­university's wartime contribution to the field, setting some ­research volunteers adrift on a lifeboat off Hyannis Port to measure how they fared on ­survival ­rations. In his 2008 book, Break Through Your Set Point: How to Finally Lose the Weight You Want and Keep It Off, he boiled it down to a numbers game: Don't lose more than 10 percent of your total body weight in any one period of dieting; do it slowly; and ­after you lose the weight, maintain that loss for at least six months, to let your body metabolically recalibrate, before attempting to lose any more weight. As Blackburn put it to me: "If you can't keep it off, don't take it off."

The fly in the ointment here is that no one has ever demonstrated that your body does physiologically "recalibrate" after you lose weight and keep it off. It may do so when less than 10 percent of body weight is lost or if the weight comes off gradually enough (one of the Australian researchers is presently testing that hypothesis). But the evidence to date is not encouraging. Even many patients who have undergone gastric-bypass surgery stay at a lower weight for a few years and then inexorably eat their way back up the scale.

But interestingly, the plateau effect that Blackburn describes is exactly what many weight-loss clinicians say their ­clients exper­ience: Weight comes off step-wise, loss being followed by a static period ­during which they decide whether it's worth tweaking their diet or exercise ­regime further in order to keep losing—without trying to white-knuckle it through hunger pangs (the revenge of the low leptin). For others, maybe it's about accepting that the ­plateau is where you're meant to be: your set point. "We'll talk about 'dream weight' or ­'wedding weight,' " Swift says about identifying goals with clients, "and then we'll do a reality analysis."

Naturally, when weight loss levels off, a lot of people panic ("The diet's stopped working!"), setting the stage for relapse and regain. Marc David tells his clients, "Let's respect the plateau, let's hang there for a while." Says Swift, "I use the term 'holding pattern,' and my clients go, 'Okay, but eventually this plane is going to land.' "

Let's say you're committed to losing more weight, and your diet is already healthy and fiber-full—what then? The clini­cians each have their own bag of tricks that speak to different aspects of meta­bolism. David emphasizes stress reduc­tion, which lowers your cortisol, the belly-fat-promoting stress hormone. Swift and Pick look first at possible food sensitivities—to gluten or to dairy products, for ­example—or at out-of-balance gut bacteria that may be righted with adjustments in diet and/or probiotic supplements.

But exercise is where the most solid science lies, the variable that likely can work to most people's advantage. Michael Rosenbaum, MD, helped design a series of experiments at Columbia University that determined that the muscles of people who've lost weight burn fewer calories during physical activity—in effect, becoming too efficient for our own good. Rosenbaum thinks there is an interesting theoretical possibility that we might be able to help outfox our uncooperative physiology via resistance exercise, typically weight training, which enlists Type 2, or "fast-twitch," muscle fibers that haven't learned to be as efficient as Type 1 "slow-twitch" muscle—but he has yet to develop evidence or data to support this notion. Marcelle Pick is also a big fan of anaerobic "interval" workouts (introducing sprints into the mix during running, swimming, cycling, or any other endurance exercise) to get more metabolic bang for the buck. And old-fashioned slow-paced aerobics—such as walking—still has plenty of clinical advocates.

The most important priority is to get ­regular exercise, and plenty of it, says Brown University's Rena Wing, PhD, who maintains a National Weight ­Control ­Registry of some 10,000 people, mostly women, who have lost 70 pounds on ­average and kept it off for up to six years. Her weight-loss winners average 2,700 calories of physical activity a week, the equivalent of walking four miles a day. "If people are physically active and then stop, they will regain the weight," Wing says bluntly. The truism that exercise isn't ­necessary to lose weight but is virtually ­essential to maintain it is, well, true.

So while weight loss, done smartly, turns out not to be hopeless, it is demanding—though that isn't the same thing as onerous, let alone impossible. "That's what we're always asked," Wing says. " 'Do these [Registry] people think they're suffering?' And the answer is no—they're very happy with these changes" in their lives and routines. Within limits, the mind can override the body, by saying goodbye to some old bad habits and, over time, embracing healthier new ones as real pleasures.

* Some text in this article has been amended from the original version that ran in our March 2012 issue.